Diesel fuel injector



Jan. 8, 1963 s. A. COLGATE DIESEL FUEL INJECTOR 2 Sheets-Sheet 1 FiledMarch 21, 1960 S. A. COLGATE DIESEL FUEL INJECTOR Jan. 8, 1963 2Sheets-Sheet 2 Filed March 21. 1960 Stte a 3,072,114 DESIRE. FUELINJECTUR Stirling A. Coigate, Livermore, Calih, assigncr of onehalf toRichard M. Colgate, Oldwiclr, NJ. Filed Mar. 21, 1960, Scr. No. 1th,.38l5 Claims. (Cl. 123-139) Such injection must be made against the highhead pressure within the cylinder and should be accurately timed withrespect to the position of the piston.

To accomplish fuel injection under the foregoing conditions, it hasheretofore been the usual practice to employ injectors which areoperated by remotely situated high pressure compressors or by mechanicalcoupling with the crankshaft of the engine. The usual compressors orother linkage between the crankshaft and fuel injectors considerablycomplicate the engine and increase the weight, bulk and proneness tobreakdown thereof.

In the case of free piston engines such as are employed in powerhammers, no crankshaft or equivalent rotary component is available todrive a fuel compressor or other linkage and operation of such engineson the diesel principle is still further complicated by the high pistonreciprocation rates characteristic of the devices. While dieseloperation has been used in free piston engines in some instances, theinjection systems have been complex, heavy and less than satisfactory.

In addition to the problems associated with driving the injectors, priordesigns have suffered from a further disadvantage in that accidentaltrapping of air in the injector fuel passages interrupts operation ofthe engine and requires that manual purging be performed. In priordesigns, difiiculty has been encountered from such factors as injectionat less than the desired pressure, carbonization of the injection nozzleand inability to function at high piston reciprocation rates.

The present invention provides a novel fuel injector which overcomes theforegoing problems, the injector being driven and timed solely by thehead pressure within the engine cylinder. No external compressor ordriving linkage is required and the injector is thus compact, light, andcapable of operation at extremely high piston reciprocation rates. Theinjector is automatically purged, injects only at a pre-determinedminimum pressure, and is relatively free from carbonization. Theinvention thus makes practical the wide-spread use of diesel operationin freepiston devices and offers considerable advantages in other formsof diesel engine.

Salient elements of the invention comprise a housing secured to thecylinder head over an opening therein, the housing having a borecommunicating with the cylinder in which bore a sliding injector pistonis disposed. The end of the injector piston which is opposite the enginecylinder bears on a fuel chamber of less diameter than the piston. Thusas the head pressure rises within the engine cylinder, in response toupward movement of the engine piston therein, the injector piston mustraise the pressure in the fuel chamber to a still higher value.Accordingly the fuel charge is pressurized for injection solely by thecylinder pressure itself, no external drive means for the injector beingrequired.

To provide for injection, a fuel passage communicates valve and noinjection will occur.

Patented Jan. 8, 1963 the fuel chamber with the cylinder head. Suchpassage is normally closed, however, by a needle valve on which aresilient element bears so that the passage will be opened for fuelinjection only upon attainment of a predetermined minimum fuel pressurewithin the chamber.

To regulate the quantity of fuel injected, the needle valve is caused toabut against a second resilient element after a selected travel of theinjector piston whereupon the valve again closes the injection passage.

Automatic purging of air trapped in the fuel chamber is provided for inthat such air is compressible and therefore the normal movement of theinjector piston does not raise the pressure within the chamber to theusual high value. Provided the force constants of the resilient elementsare of appropriate values, the relatively low fuel chamber presure willnot be suificient to open the needle Owing to the relatively low backpressure within the fuel chamber, the injector piston will move past itsnormal stopping point, i.e. the point at which contact is made with thesecond resilient element. Such abnormal movement is arranged to uncovera vent passage through which the trapped air within the chamber isejected.

Thus the invention overcomes the problems herebefore discussed, theinjector being self-actuated and self-purging and directly responsive tomovement of the engine piston within its cylinder.

It is therefore an object of this invention to provide a superior fuelinjector for internal combustion engines which injector is driven byhead pressure variation within the cylinder of said engine.

It is an object of this invention to provide a diesel fuel injectorwhich is compact, self-actuated and which requires no external drivingmeans or high pressure lines.

It is a further object of the invention to provide a fuel injector foran engine which injector is tuned to the head pressure of said engineand which injects fuel only at a predetermined minimum pressure.

It is an object of the invention to provide a diesel fuel injectorparticularly suited for use with engines of the free-piston class.

It is still a further object of this invention to provide a fuelinjector having automatic provision for purging air entrapped in thefuel passages.

It is an object of the invention to provide a diesel fuel injectorcapable of operation at extremely high piston reciprocation rates.

it is another object of this invention to provide a selfactuated,self-purging, fuel injector which is compact, light and relatively freefrom carbonization.

The invention, both as to its organization and method of operation,together with further objects and advantages thereof, will best beunderstood by reference to the following specification taken inconjunction with the accompanying drawing, in which:

FIGURE 1 is a longitudinal section view showing an exemplary embodimentof the invention mounted on the head of a free piston engine,

FIGURE 2 is a view taken along line 2-2 of FIGURE 1 and showing thenozzle region of the injector,

FIGURE 3 is a cross section view taken along line 3-3 of FIGURE 1 andfurther clarifying the structure of the injector, and

FIGURE 4 is a section view taken along line 44 of FIGURE 1 and showingmeans by which the quantity of fuel injected into the cylinder iscontrolled.

Referring now to the drawing and more particularly to FIGURES 1 and 2thereof, there is shown a portion of the cylinder ll of a free-pistonengine which engine may be, for example, of the type disclosed in theaforementioned co-pending application Serial No. 623,034. An enginepiston 12 is slidably mounted in the cylinder and reciprocates thereinin the conventional manner, a rise of the piston acting to compress andheat air in the head region 113 of the piston so that the subsequentinjection of combustible fuel will produce a downward power stroke.

To provide for the mounting of the fuel injector, an axial passage isformed in the top of cylinder 11, such passage having a broad uppersection 14 and a narrower lower section 16 which opens into the cylinderhead 13. To form a portion of an injector housing, a generallycylindrical injector base member 17 is fitted coaxially within upperpassage section 14-, an annular seal 18 being coaxially disposed aroundthe underside of the base member.

To secure base member 17 to the cylinder 11, an annular flange 1'9 isformed at an intermediate position on the base member which flange abutsthe top surface of the cylinder. As shown in FIGURES l and 3 inconjunction, a plurality of bolts 21 are transpierced through flange 19and threadably engaged in the cylinder head, the bolts beingequi-angularly distributed around the flange.

Base member 17 is provided with an axial bore having an upper section22, a long intermediate section 23 and a short lower section 24 whichsections are of progressively less diameter and the lowermost of whichsections 2d has a diameter slightly less than that of the lower section16 of the passage in the cylinder head.

The upper section 22 of the passage in base member 17 is threaded toreceive the threaded lower end of a cylindrical injector body 26, theinjector body being thus mounted in the base member in coaxialrelationship therewith and forming another portion of the housing. Acylindrical extension 2'7 projects axially from the lower end of theinjector body within passage section 23, the extension being of slightlyless diameter than the lower bore section 24 of the base member.

To define a fuel chamber at the lower end of extension 2'7 and toamplify and transmit the cylinder head pressure to such chamber, aninjector piston 28 is coaxially disposed within the base member 17.Piston 2d is provided with an upper annular portion 29 disposedcoaxially around extension 27 within the intermediate passage section 23of the base member, the annular portion 29 being of less length in theaxial direction than passage section 23 so that the piston may slideupwardly in response to a rise of pressure within cylinder 11. Piston 28is further provided with a cylindrical lower portion 31 which is coaxialwith portion 29 and of lesser diameter and which extends downwardlythrough bore section 24 of the base member 17 and into passage 16 on thecylinder head.

The lower end of portion 31 of the injector piston is closed by an endmember 32 which member has a narrow axial passage 33 flared at the lowerend to provide a fuel injection nozzle. The region within the pistonbetween end member 32. and the lower end of injector body extension 27thus forms a fuel chamber 34; in which upward movement of the pistonwill act to raise the fuel primers. An annular seal 36 is mounted in theinterior wall of base member bore section 23 to form a gas tight sealarou d the piston which seal thus defines the area against which thehead pressure in the cylinder acts. As will hereinafter be discussed inmore detail, the cross section area of the fuel chamber 34 isconsiderably less than that enclosed by sea'v 36 so that a given headpressure within the cvlinder it acts to create a greater pressure withinthe fuel chamber.

To supply fuel to chamber 34, a check valve fitting 37 is threadablyengaged in the wall of injector body 26 and pas a e extends from thecheck valve to the fuel chamber through extension 27. Check valve 37 isa ra'n ed to limit fuel flow to a direction towards the chamber 34 andis connected, through a suitable conduit 39, with a supply of fuel.

To eliminate unwanted resistance to movement of piston 2d, a ventpassage 41 is provided in the lower portion of the injector body 26which passage communicates with the upper end of base passage 23 andwhich opens at the side of too injector body.

Considering now means by which the injection passage 33 at tne bottom ofthe chamber 34 is held closed until a desired minimum fuel pressure hasbeen achieved, and means by which automatic purging of air from the fuelchamber is effected, an axial bore is provided in the injector body 26which bore has a broad upper section 42 and a narrow lower portion 43which lower portion is of less diameter than the fuel chamber and whichpasses through extension 27 and opens into the chamber.

A long cylindrical needle valve shaft 4-4 is slidably disposed along theaxis of the injector body, the shaft having a lower portion conformingin diameter to bore 4-3 and extending therethrough. An annular retainer46 is threadably engaged in the upper end of bore section 42, in coaxialrelationship therein, and is provided with an axial guide passage 47into which the upper end of the valve shaft 44 extends.

A step 4.3 is formed near the lower end of the valve shaft 4- 3 and theterminal portion 45* thereof is of reduced diameter. The extreme lowerend of the shaft 44 is provided with a conical point 51 and a matchingconical valve seat 52 is formed in piston end member 32 at the top ofinjection passage 33. The members thus form a needle valve controllingthe release of fuel from chamber 34 into the engine cylinder.

To yieidably hold point 51 against the valve seat 52, a flange 53 isformed on valve shaft near the base of bore 42 in the injector body. Acompression spring 54 is disposed coaxiaily around the upper portion ofshaft 4- and bears against the flange 53 and retainer 46. Spring 54 thusexerts a downward force on the valve shaft 44 and tends to holdinjection passage 33 closed. When the pressure within the fuel chamber34 rises to an appropriate value, however, the fluid pressure againststep 48 of the valve shaft will lift the shaft against the force ofspring 54 and fuel injection through passage 33 will occur. Thus theinjection pressure may be predetermined by the force constant of thespring 54.

Considering now the throttle mechanism by which the quantity of fuelinjected into the cylinder 11 is controlled, a tubular sleeve '56 isslidably disposed in-bore 42 of the injector body in coaxialrelationship therein. Sleeve 56 is of less length in the axial directionthan bore 42 and is provided with an annular rim 57 at the lower end,which rim extends radially inward to overlap the flange 53 on valveshaft 44. Thus upward movement of the valve shaft 44 will cause flange53 to abut against rim 57.

A second compression spring 8 is disposed within bore 42 in coaxialrelationship therein, the spring 53 extendingbetween the sleeve rim 57and retainer 4-6. As will hereinafter be discussed in more detail,spring 58 is selected to exert a force against valve shaft 44, afterabutment of flange 53 against sleeve rim 57, suilicient to hold theneedle point 51 against valve seat '52 and thus to terminate fuelinjection. Thus the amount of fuel injected is determined by thelongitudinal position of sleeve 56 in bore 42,- i.e. by the initialclearance between flange and rim 57.

To establish, and selectively vary, this clearance, a rotatable throttleshaft 59 is transpierced through the side wall of the injector body 26near the lower end of bore 42 thereof, a boss 61 being formed on theouter surface of the injector body to provide a journal for the shaft.An annular retainer 62 is secured on shaft 59 at the outer end of boss51 by a set screw 63 and an annularwasher 64 is disposed around theshaft within bore 52. Referring now to FIGURE 4 in conjunction with PEG-URE 1, an ovate cam as is secured to the end of shaft 5:9 within bore 42and beneath the lower rim 57 of sleeve 56. The sleeve 5'6 will be forceddownwardly to abut against the uppermost surface of the cam 66 by spring58. Accordingly the turning of cam 66, means of shaft 59, will act toselectively vary the position of sleeve 56 and will therefore regulatethe size of the fuel charge injected into cylinder 11. The shaft 59 maybe operated by any of various throttle linkages well known to thoseskilled in the art.

Considering now the means by which automatic purging of air in the fuelchamber 34 is effected, a vent passage 67 is provided in the lower endof the injector body one end of which passage opens at the side of theinjector body, preferably into a fitting 68 and vent pipe 69. Ventpassage 67 extends downwardly within extension 27 and opens into bore 43thereof at a level immediately above the maximum height to which step 48of valve shaft 44 is elevated during a normal fuel injection cycle. Thislevel is that occupied by the step 48 when valve shaft flange 53 abutssleeve rim 57 with cam 66 turned to pro vide maximum fuel injection.

Thus the portion of valve shaft 44 immediately above step 48 willnormally block the vent passage 67 from the fuel chamber 34 during allstages of operation. In the event air is present in the chamber 34,however, the chamber pressure is much less than normal for a givenupward force on the injector piston 28. The force exerted on step 48 ofthe valve shaft 44 is thus less than normal and is insuflrcient toovercome Spring 54 and lift the needle valve 51 from seat 52.Accordingly the piston 28 rises without injection occurring and carriesthe needle valve shaft 44 upward. Since the back pressure against theinjector piston 23 is relatively small, the piston continues to travelupwardly even after abutment of flange 53 against sleeve rim 57 inasmuchas the springs are selected to exert a combined force on the valve shaft44 which is less than the upward force exerted on piston 28 by the headpressure within cylinder 11.

Thus the valve shaft 44 rises above the usual maximum elevation thereofuncovering vent passage 67 and allowing the trapped air to escapethrough vent pipe 69. Subsequent downward movement of the injectorpiston 28, as engine piston 12 descends in cylinder 11, draws a newcharge of fuel into chamber 34 and operation proceeds in the usualmanner.

Considering now the general operation of the injector as well as typicalparameters thereof, it may be seen that the rise of engine piston 12within cylinder 11 causes a high pressure to be exerted against theunderside of injector piston 28. The effect of such pressure will be toraise the fuel pressure within chamber 34 to a much higher value owingto the area ratio of seal 36 relative to the chamber cross-section. Afuel chamber pressure of 5000 lbs. per square inch will be found typicalfor an area ratio of :1.

The high fuel pressure pushes upwardly on the still smallercross-sectional area of needle valve shaft 44. The shaft 44 is held downby the force of spring 54 which is selected to have a force constantjust sufficient to counterbalance the desired fuel injection pressure,for example an injection pressure of 5000 lbs. per square. inch. Whenthefuel pressure reaches this value, the needle valve 51 rises from seat 52allowing the fuel to travel downwardly through passage 33 and enter thecylinder 11.

As fuel is being injected, the injector piston 28 rises and the needlevalve 51 must continue ahead of the piston to permit injection. After aselected upward travel of the valve shaft 44, determined by the settingof throttle shaft 59 and cam 66, flange 53 abuts sleeve rim 57 and thusthe second spring 58 resists further upward movement of the valve shaft.Spring 58 may have a force constant of the order of two times greaterthan that of spring 54 so that to continue injection the fuel pressurewould have to exert a force on shaft 44 greater than the combined forceof the two springs. A fuel pressure of 15,000 pounds per square inchwould be require for example, which value is higher than that which willbe reached. Accordingly fuel injection stops when flange 53 contacts thesleeve rim 57.

When the pressure in cylinder 11 is reduced by downward movement of theengine piston 12, spring 54 drives the valve shaft 44 and injectorpiston 28 downward and the injector returns to the initial condition.

It should be understood that an additional manually openable valved ventpassage can be provided in the in jector body 26 which passage maycommunicate with the fuel chamber 34 and serve for manual purging of airfrom the chamber prior to starting. Such provision may be found usefulwhere the injector is used with an engine that must start after a singleupward movement of the engine piston, such as some forms of free pistonengine,

but will not be needed where the usual multiple cycle starting isavailable.

It will be apparent to those skilled in the art that many variations inthe configuration and arrangement of elements of the invention arepossible within the spirit and scope of the invention. Thus while theinvention has been disclosed with respect to a single exemplaryembodirnent, it is not intended to limit the invention except as definedin the following claims.

What is claimed is:

1. In a fuel injector for an internal combustion engine which engine isof the class having a cylinder and reciprocating engine piston therein,the combination comprising means defining a fuel chamber at the head ofsaid cylinder which chamber is communicated with said cylinder through anarrow injection passage, a movable injector piston disposed at the headof said cylinder which injector piston has a first end exposed to thehead pressure of said cylinder and which has a smaller surface oppositesaid first end which surface bears on said fuel chamber to raise thepressure therein to a value higher than said head pressure, a valveelement movable to close said injection passage from said fuel chamber,said valve element being exposed to the pressure within said chamberacting in a direction to move said element to open said passage, a firstresilient means bearing against said valve element in a direction toclose said passage whereby injection of fuel into said cylinder does notoccur until the pressure therein reaches a value capable of overcomingthe force of said resilient means on said valve element, a secondresilient means bearing against said valve element only after a degreeof travel thereof, and means forming a vent passage communicating withsaid fuel chamber only after travel of said valve element past the pointof engagement with said second resilient means.

2. In a mechanism for injecting fuel into an internal combustion enginewhich engine is of the class having a cylinder and reciprocating enginepiston therein, the combination comprising means forming a fuel chamberat the head of said cylinder which chamber is communicated with saidcylinder through a narrow injection passage, a movable injector pistondisposed at the head of said cylinder which injector piston has a firstend exposed to the head pressure of said cylinder and which has asmaller end portion opposite said first end which smaller end portionbears on said fuel chamber to elevate the pressure therein above that ofsaid cylinder head, a sliding needle valve having a stepped end portionprojecting into said fuel chamber towards said injection passagetherein, a first resilient element urging said needle valve towards saidinjection passage, 21 second resilient element positioned to engage saidneedle valve after a predetermined retraction of said valve from theinitial position hereof and, exerting a force on said needle valve inthe direction of said injection passage, and means forming a ventchannel openable into said fuel chamber upon retraction of said needlevalve past the point of engagement with said resilient element wherebyair trapped within said chamber is released.

3. A mechanism for injecting fuel into an internal combustion enginesubstantially as described in claim 2 and comprising the furthercombination of means for controllably adjusting said second resilientelement to engage said needle valve after varying degrees of retractionthereof whereby the quantity of fuel injected into said cylinder may becontrolled.

4. A fuel injector for an internal combustion engine which engine is ofthe class having a cylinder and reciprocable engine piston therein andwhich cylinder has an opening at the head thereof, said injectorcomprising a housing mountable over said opening in said cylinder andhaving a stepped bore aligned coaxially with said opening, said borehaving a broad section in proximity to said cylinder and a narrowsection more remote from said cylinder, said housing having a ventpassage communicating with an intermediate point in said narrow sectionof said bore, a cylindrical injector piston slidingly disposed in saidbroad section of said bore in coaxial relationship therein, saidinjector piston having a first end facing said cylinder and having anopposite end surface of reduced area facing said narrow section of saidbore, said injector piston being pierced by a narrow axial fuelinjection passage, means defining a contractable fuel chamber withinsaid broad section of said bore between said opposite end surface ofsaid injector piston and said narrow section of said bore which chamberhas said opposite end surface of said injector piston as one bound-' 8.in the direction of said cylinderto close said passage, and a secondspring positioned to engage said needle valve upon retraction of saidreduced extremity there of to the vicinity of said intermediate point insaid narrow section of said bore, said second spring exerting anadditional force on said needle valve in the direction of said cylinder.

5. A fuel injector for an internal combustion engine substantially asdescribed in claim 4 wherein said needle valve projects from said narrowsection of said bore at the end thereof remote from said fuel chamberand is provided with a flange and wherein said housing is formed with acoaxial tubulation around said flanged projection of said needle valveand comprising the further combination of a slidable sleeve disposedcoaxially within said tubulation and extending radially inwardly to beabutted by said flange on said needle valve after retracting movementthereof, said second spring being disposed coaxially within saidtubulation and urging said sleeve in the direction of said cylinder, anda controllably rotatable cam bearing against said sleeve to adjust thelongitudinal position thereof Within said tribulation.

References fitted in the file of this patent UNITED STATES PATENTSFrance Aug. 7, 1939

1. IN A FUEL INJECTOR FOR AN INTERNAL COMBUSTION ENGINE WHICH ENGINE ISOF THE CLASS HAVING A CYLINDER AND RECIPROCATING ENGINE PISTON THEREIN,THE COMBINATION COMPRISING MEANS DEFINING A FUEL CHAMBER AT THE HEAD OFSAID CYLINDER WHICH CHAMBER IS COMMUNICATED WITH SAID CYLINDER THROUGH ANARROW INJECTION PASSAGE, A MOVABLE INJECTOR PISTON DISPOSED AT THE HEADOF SAID CYLINDER WHICH INJECTOR PISTON HAS A FIRST END EXPOSED TO THEHEAD PRESSURE OF SAID CYLINDER AND WHICH HAS A SMALLER SURFACE OPPOSITESAID FIRST END WHICH SURFACE BEARS ON SAID FUEL CHAMBER TO RAISE THEPRESSURE THEREIN TO A VALUE HIGHER THAN SAID HEAD PRESSURE, A VALVEELEMENT MOVABLE TO CLOSE SAID INJECTION PASSAGE FROM SAID FUEL CHAMBER,SAID VALVE ELEMENT BEING EXPOSED TO THE PRESSURE WITHIN SAID CHAMBERACTING IN A DIRECTION TO MOVE SAID ELEMENT TO OPEN SAID PASSAGE, A FIRSTRESILIENT MEANS BEARING AGAINST SAID VALVE ELEMENT IN A DIRECTION TOCLOSE SAID PASSAGE WHEREBY INJECTION OF FUEL INTO SAID CYLINDER DOES NOTOCCUR UNTIL THE PRESSURE THEREIN REACHES A VALUE CAPABLE OF OVERCOMINGTHE FORCE OF SAID RESILIENT MEANS ON SAID VALVE ELEMENT, A SECONDRESILIENT MEANS BEARING AGAINST SAID VALVE ELEMENT ONLY AFTER A DEGREEOF TRAVEL THEREOF, AND MEANS FORMING A VENT PASSAGE COMMUNICATING WITHSAID FUEL